“Shook Ones Part II,” from “The Infamous” album, is Mobb Deep’s most-cherished hit, so iconic that when Eminem needed a draught of sonic courage in “8 Mile,” he turned to it, with its distinctive tick-tock drums and dark, minor-key bass line.

Except, it turns out, the source of that bass line wasn’t a bass line at all, one reason the sample eluded discovery. The longer “Shook Ones Part II” kept its secrets, the more it became a holy grail for sample seekers, complete with debated theories and false leads. In solving this cold case, Bronco (born Timon Heinke) and his revelation harkens to a seemingly bygone era of competitive sampling and sourcing.

In the late 1980s, as affordable digital samplers such as E-mu’s SP-1200 and Akai’s MPC-60 entered the market, beatmakers discovered the creative potential of looping and manipulating bits and pieces of music from other artists’ recordings, called “samples,” to build new songs. They sought out unused sounds on increasingly obscure records to stay ahead of their peers — and possibly copyright attorneys — and sample hounds followed just as intensely. The adage that “knowledge is power” gave samples cultural capital — DJs could build sets using “originals” while vinyl sellers could mint small fortunes by selling records sporting “known” samples.